image copyright and adsens

Hi,

How google can know if I have the right of the images I use ?

For now I use royalty-free image but it became a bit more complicated to find nice pics and pay are disproportionately expensive...
Any solutions or good free stock ? and you care about that ?

I think I'll get the gettyimage without paying, I respect the work of others but pay several hundred dollars every 3 years by pic is not for me

Thanks in advance